A. Field of the Invention
The present invention relates generally to vacuum cleaners and, more particularly, to a vacuum cleaner having an electronic control module that is shielded to provide immunity from electrostatic discharges.
B. Description of the Prior Art
Modern-day vacuum cleaners often employ electronic controls in the form of low voltage electronic components mounted on circuit boards. These controls can be damaged or rendered inoperative by inadvertent high voltage electrostatic discharges, such as those accumulated on the body of a user. When the electronic controls of a vacuum cleaner are touched by a user, an inadvertent high voltage static electrical discharge may occur with possible resultant damage to the sensitive electronic components. The vacuum cleaner of the present invention is concerned with the minimization of any such damaging static discharges.
A number of prior art patents have been directed to preventing electrical damage to sensitive electronic components. For example, U.S. Pat. No. 3,648,108 discloses a non-conductive carrier or package for a dual in-line integrated circuit having fourteen electrical leads extending therefrom. The carrier includes a conductive shunt resiliently engaging and, therefore, electrically shorting together the fourteen leads of the integrated circuit, thereby to protect the integrated circuit against possible damage due to static discharge from external sources.
U.S. Pat. No. 3,774,075 similarly is directed to a non-conductive carrier or package for integrated circuits having multiple leads. The carrier includes a conductive shunt for electrically shorting together the conductive leads, thereby reducing the possibility of damage to the integrated circuit as a result of static electricity.
U.S Pat. No. 4,303,960 is directed to a method and structure for protecting a tactile or touch operated keyboard type switch from damage due to a static electrical discharge initiated by the proximity of the finger of a human operator to the switch contacts. A layer of grounded, electrically conductive material is disposed adjacent the switch contacts to intercept any electrostatic discharge from an operator's finger and to conduct static current to ground, thereby bypassing the switch contacts and the associated electronics.
Another U.S. Pat. No. 4,404,615 discloses an "antistatic container" for packaging and shipping electronic circuit boards. The container includes a conductive liner electrically connected to a ground plane to dissipate electrostatic charges and thereby protect the electronics mounted on the circuit boards contained within the container.
U.S. Pat. No. 4,565,288 also discloses a container for integrated circuit boards having a plurality of downwardly depending electrical leads. The container includes conductive inserts formed therein for dissipating static electricity, thereby to minimize possible damage to the components on the circuit boards.
Another U.S. Pat. No. 4,602,311 discloses a method and apparatus for isolating a metallic fastener connected to a plastic housing from the electronic components disposed within the housing. Specifically, an insulating vault with a well portion is formed within the housing; and the fastener is received and retained within the vault and thereby isolated from the sensitive electronic circuitry within the plastic housing.
U.S. Pat. No. 4,633,364 is directed to a so-called static shock eliminator in which a high electrical resistance plate is disposed adjacent a grounded object, such as a metallic doorknob, handle or key cylinder. A surface on the plate is adapted to be contacted by a person at a point spaced from the grounded object, thereby to dissipate static charges.
None of the aforementioned patents discloses or suggests an effective method or apparatus for protecting sensitive electronic components mounted on a circuit board within a control module of a vacuum cleaner from damage or destruction due to high voltage static electrical discharges.